Variable-area capacitor structure, comb grid capacitor accelerometer and comb grid capacitor gyroscope

Abstract

The present invention relates to a variable-area capacitor for a micromechanical sensor, a micromechanical comb grid capacitor accelerometer and a micromechanical comb grid capacitor gyroscope. Among them, the variable-area capacitor structure comprises of a movable and a fixed electrodes in each capacitor unit; a front surface of aforesaid movable electrode is parallel to that of aforesaid fixed electrode; the front surface of aforesaid movable electrode is in a rectangular shape, and the front surface of the fixed electrode is in a triangular or sawteeth shape or the front surface of the movable electrode is in a triangular or sawteeth shape, and the front surface of the fixed electrode is in a rectangular form; the triangular front surface is only overlapped with one long side of aforesaid rectangular front surface. Micromechanical sensors with variable-area capacitor structures of the invention can adjust elasticity coefficient as compared with present technology.

The invention claimed is: 
     
       1. A variable-area capacitor structure, comprising a movable electrode and a fixed electrode in each capacitor unit, wherein a front surface of the movable electrode is parallel to a front surface of the fixed electrode, characterized in that: the front surface of the movable electrode is in a rectangular shape, and the front surface of the fixed electrode is in a triangular shape or a sawteeth shape; or the front surface of the movable electrode is a triangular shape or a sawteeth shape, and the front surface of the fixed electrode is in a rectangular shape; the triangular front surface is only overlapped with one long side of the rectangular front surface; vertical distance between the movable electrode and the fixed electrode remains unchanged, and comparative movement between the movable electrode and the fixed electrode is parallel movement; wherein the movable electrode moves parallelly along a vertical direction of the one long side of the rectangular front surface that is overlapped with the triangular front surface; wherein a voltage is imposed between the movable electrode and the fixed electrode, so that an equivalent elasticity coefficient is produced and the equivalent elasticity coefficient is adjusted by adjusting the voltage imposed; and wherein the equivalent elasticity coefficient of the capacitor structure is constant when the voltage difference between fixed electrode of the unit and movable electrode is fixed and structure parameter and quantity of the capacitor structure are predetermined. 
     
     
       2. The variable-area capacitor structure according to  claim 1 , which is characterized in that each saw tooth of the sawteeth shape front surface is in a triangular shape, and is only overlapped with one long side of the rectangular front surface. 
     
     
       3. The variable-area capacitor structure according to  claim 1 , which is characterized in that each saw tooth of the sawteeth shape is in a trapezoid shape, and is only overlapped with one long side of the rectangular front surface; whereas overlapped part is in a triangular form. 
     
     
       4. The variable-area capacitor structure according to  claim 1 , which is characterized in that each saw tooth of the sawteeth shape front surface is in a trapezoid form, and is only overlapped with one long side of the rectangular front surface; whereas overlapped part is in a trapezoid shape, a bottom side of the trapezoid shape is parallel to a long side of the rectangular front surface. 
     
     
       5. A comb grid capacitor accelerometer with adjustable elasticity coefficient, which is characterized in that: an electric tuning variable-area capacitor for regulation of elasticity coefficient is distributed in a sensitive direction of the accelerometer; in each unit capacitor of the electric tuning variable-area capacitor, the front surface of the movable electrode is parallel to the front surface of the fixed electrode; the front surface of the movable electrode is in a rectangular shape, and the front surface of the fixed electrode is in a triangular shape or a sawteeth shape or the front surface of the movable electrode is in a triangular shape or sawteeth shape, and the front surface of the fixed electrode is in a rectangular shape; the triangular front surface is only overlapped with one long side of the rectangular front surface; vertical distance between the movable electrode and the fixed electrode remains unchanged, and comparative movement between the movable electrode and the fixed electrode is parallel movement; wherein the movable electrode moves parallelly along a vertical direction of the one long side of the rectangular front surface that is overlapped with the triangular front surface; wherein a voltage is imposed between the movable electrode and the fixed electrode, so that an equivalent elasticity coefficient is produced and the equivalent elasticity coefficient is adjusted by adjusting the voltage imposed; and wherein the equivalent elasticity coefficient of the capacitor structure is constant when the voltage difference between fixed electrode of the unit and movable electrode is fixed and structure parameter and quantity of the capacitor structure are predetermined. 
     
     
       6. The comb grid capacitor accelerometer with adjustable elasticity coefficient according to  claim 5 , characterized in that each saw tooth of the sawteeth shape front surface is in a triangular form, and is overlapped with one long side of the rectangular front surface. 
     
     
       7. The comb grid capacitor accelerometer with elasticity coefficient available for regulation according to  claim 5 , which is characterized in that each saw tooth of the sawteeth shape front surface is in a trapezoid shape, and is only overlapped with one long side of the rectangular front surface; the overlapped part is in a triangular shape. 
     
     
       8. The comb grid capacitor accelerometer with adjustable elasticity coefficient available for regulation according to  claim 5 , which is characterized in that each saw tooth of the sawteeth shape front surface is in a trapezoid shape, and is only overlapped with one long side of the rectangular front surface; the overlapped part is in a trapezoid shape, a bottom side of the trapezoid shape is parallel to a long side of the rectangular front surface. 
     
     
       9. A comb grid capacitor gyroscope with adjustable resonance frequency, which is characterized in that an electric tuning variable-area capacitor is distributed in a drive direction or a sense direction of the gyroscope; a front surface of a movable electrode in each unit capacitor of the electric tuning variable-area capacitors is parallel to a front surface of a fixed electrode of the unit capacitor, which is characterized in that the front surface of the movable electrode is in a rectangular shape, and the front surface of the fixed electrode is in a triangular shape or a sawteeth shape or the front surface of the movable electrode is in a triangular shape or a sawteeth shape, and the front surface of the fixed electrode is in a rectangular form; the triangular front surface is only overlapped with one long side of the rectangular front surface; vertical distance between the movable electrode and the fixed electrode remains unchanged, and comparative movement between the movable electrode and the fixed electrode is parallel movement; wherein the movable electrode moves parallelly along a vertical direction of the one long side of the rectangular front surface that is overlapped with the triangular front surface; wherein a voltage is imposed between the movable electrode and the fixed electrode, so that an equivalent elasticity coefficient is produced and the equivalent elasticity coefficient is adjusted by adjusting the voltage imposed; and wherein the equivalent elasticity coefficient of the capacitor structure is constant when the voltage difference between fixed electrode of the unit and movable electrode is fixed and structure parameter and quantity of the capacitor structure are predetermined. 
     
     
       10. The comb grid capacitor gyroscope with adjustable resonance frequency according to  claim 9 , which is characterized in that each saw tooth of the sawteeth shape front surface is in a triangular shape, and is only overlapped with one long side of the rectangular front surface. 
     
     
       11. The comb grid capacitor gyroscope with adjustable resonance frequency according to  claim 9 , which is characterized in that each saw tooth of the sawteeth shape front surface is in a trapezoid shape, and is only overlapped with one long side of the rectangular front surface; the overlapped part is in a triangular shape. 
     
     
       12. The comb grid capacitor gyroscope with adjustable resonance frequency according to  claim 9 , which is characterized in that saw tooth of the sawteeth shape front surface is in a trapezoid shape, and is only overlapped with one long side of the rectangular front surface; the overlapped part is in a trapezoid shape, a bottom side of the trapezoid shape is parallel to the rectangular front surface. 
     
     
       13. The variable-area capacitor structure according to  claim 1 , wherein the equivalent elasticity coefficient along axis X is as follows:
     k   x   =−dF   x   /dx=−V   2   ·ξ·m/ 2 /h/f,    
 wherein S (overlapped area)=m·(e−x)·(e−x)/2/f; 
 C (capacity)=ξ·S/h=ξ·m·(e−x)·(e−x)/2/h/f; 
 F x  (electrostatic force along axis X)=V 2 /2·dC/dx=V 2 /2·ξ/h·dS/dx; and 
 wherein V refers to the voltage difference between the fixed electrode and the movable electrode; m refers to the length of bottom side of the fixed electrode of the triangular unit; f refers to the height of the fixed electrode of the triangular unit; x refers to displacement of the movable electrode of the unit along X axis.